1. Field of the Invention
The present invention relates to a system and method for transferring a command set for controlling an image forming process from a host apparatus to an image forming apparatus.
2. Description of the Related Art
An image forming apparatus (e.g., a graphics card or the like) which is connected to a personal computer or the like by a bus to achieve an expanded image forming process is well known. Upon reception of a read instruction (including a transfer size and a storage address) for commands (image forming command set) relating to an image forming process from a CPU (host CPU (Central Processing Unit)) of a personal computer or so, the image forming apparatus reads the image forming command set from a main memory device in the personal computer or so according to the contents of the read instruction. Then, the image forming apparatus executes a command process (i.e., image forming process) according to the read image forming command set.
In general, each command (image forming command) in the image forming command set includes a context command and an object command. A context (also called graphics context) command is a command relating to setting or the like of an operation mode needed for image forming. For example, a top address on a memory for each buffer (buffer for outputting an image forming result, buffer for imaging a font, or the like), a pixel size and color format (RGB, YUV or the like), or a color conversion matrix parameters and LUT (LookUp Table), or the like are equivalent to a context command.
An object command is a command relating to setting or the like for specifying an image forming target. For example, coordinate data and coordinate conversion matrix parameters or the like for executing a process for enlargement, reduction, rotation, etc. are equivalent to an object command.
The conventional image forming apparatus reads whole image forming command sets including a context command set from the main memory device one after another. Therefore, the amount of data (transfer size) at the time the image forming apparatus executes single reading is large, which is a factor to prohibit improvements on the efficiency of data transfer.
For example, a technique directed to reducing the load at the time of data transfer relating to transfer of an image forming command set is proposed in Japanese Patent Application Laid-Open No. 2003-50774.